diff --git a/src/propeller/gp.cljc b/src/propeller/gp.cljc
index 3c89f00..7c87229 100644
--- a/src/propeller/gp.cljc
+++ b/src/propeller/gp.cljc
@@ -61,7 +61,7 @@
             (prn {:total-test-error
                   (:total-error (error-function argmap (:testing-data argmap) best-individual))})
             (if (:simplification? argmap)
-              (let [simplified-plushy (simplification/auto-simplify-plushy argmap (:plushy best-individual) (:simplification-steps argmap) error-function (:training-data argmap) (:simplification-k argmap) (:simplification-verbose? argmap))]
+              (let [simplified-plushy (simplification/auto-simplify-plushy argmap (:plushy best-individual) (:simplification-steps argmap) error-function (:training-data argmap) (:simplification-k argmap) (:simplification-k-prob argmap) (:simplification-verbose? argmap))]
                 (prn {:total-test-error-simplified (:total-error (error-function argmap (:testing-data argmap) (hash-map :plushy simplified-plushy)))}))))
         ;;
         (>= generation max-generations)
diff --git a/src/propeller/problems/simple_regression.cljc b/src/propeller/problems/simple_regression.cljc
index dd0a063..d0f153e 100644
--- a/src/propeller/problems/simple_regression.cljc
+++ b/src/propeller/problems/simple_regression.cljc
@@ -66,25 +66,18 @@
   [& args]
   (gp/gp
     (merge
-     {:instructions             instructions
-      :error-function           error-function
-      :training-data            (:train train-and-test-data)
-      :testing-data             (:test train-and-test-data)
-      :max-generations          500
-      :population-size          500
-      :max-initial-plushy-size  100
-      :step-limit               200
-      :parent-selection         :lexicase
-      :case-queue?              false
-      :case-step                1
-      :downsample-size          10
-      :tournament-size          5
-      :umad-rate                0.1
-      :variation                {:umad 0.5 :crossover 0.5}
-      :elitism                  false
-      :simplification?          true
-      :simplification-steps     100
-      :simplification-k         5
-      :simplification-verbose?  true}
-     (apply hash-map (map #(if (string? %) (read-string %) %) args))))
+      {:instructions             instructions
+       :error-function           error-function
+       :training-data            (:train train-and-test-data)
+       :testing-data             (:test train-and-test-data)
+       :max-generations          500
+       :population-size          500
+       :max-initial-plushy-size  100
+       :step-limit               200
+       :parent-selection         :lexicase
+       :tournament-size          5
+       :umad-rate                0.1
+       :variation                {:umad 0.5 :crossover 0.5}
+       :elitism                  false}
+      (apply hash-map (map #(if (string? %) (read-string %) %) args))))
   (#?(:clj shutdown-agents)))